Earthmoving machines are well-known types of construction equipment, and are generally used for digging, grading, or otherwise placing dirt, rocks, or other material involved in the building of a construction project, according to a jobsite plan. Common types of earthmoving machines are excavators, bulldozers, graders, front-end loaders, backhoes, trenchers, compactors, screeds, pavers, and the like.
When digging a trench or a ditch, such earthmoving machines need to be guided with respect to using their working tools to create a desired dig elevation or a desired profile for a ditch or trench. Modern electronic devices are typically used to assist the operator of such earthmoving machines. In conventional systems, various different types of sensing components typically are individually installed at different locations on the machine itself during an “installation” step. Each of those sensing components then must be calibrated to the particular machine member that it has been mounted to, and the geometric dimensions of the instrumented members must be measured and entered into system memory during a “machine calibration” step. Finally the operator must align the on board position sensor(s) to jobsite coordinates during a “benching” step, before the operator can perform any useful tasks.
Construction projects are built in more than one stage. Before any digging can be satisfactorily performed, the jobsite must be surveyed and marked (or “staked”). Laying out the surveyed jobsite to create the physical benchmarks can be considered a “Stage One” phase of the project. After Stage One is completed, the digging can begin; this can be considered a “Stage Two” of the project. For “old” jobsites where the buildings and utility lines are already in existence, Stage One includes “finding” certain important objects before the Stage Two digging begins, especially if the important objects are below ground level.
In U.S. Pat. No. 8,363,210 (by Montgomery), an excavator machine is instrumented with a laser rangefinder mounted on the dipperstick, with gravity sensors mounted under the cab, and with angle encoders mounted at the joint of the boom and stick, and at the joint of the stick and bucket. After these sensors are installed on the machine, all the sensors must be calibrated to the machine itself before the appropriate machine dependent set-offs can be determined and the system can be used. The Montgomery patent discloses an electronic system that assists in performing some of the tasks for Stage One, noted above. The electronic system is told the jobsite ground coordinates of where a “feature” should be located, and then the excavator physically approaches that feature and aims the laser rangefinder at the precise expected location of that feature. Some features are underground, so the laser rangefinder is also used to determine how far below the ground level that feature is supposed to be. The purpose of all this is so the excavator machine operator can easily find and then properly identify that feature. Once that specific feature has been found and identified, the electronic system can determine the three-dimensional coordinates of that “found feature,” and can electronically mark that set of coordinates so this data can be loaded by engineers into an “as-built drawing.” In essence, Montgomery discloses a new type of surveying system for a completed, or nearly-completed, construction site. All of the sensors in Montgomery's system must be calibrated to the machine itself.